Chapter 5, Analysis: Dynamic Modeling

1. Chapter 5, Analysis: Dynamic Modeling

2. Outline of the Lecture • Dynamic modeling • Sequence diagrams • State diagrams • Using dynamic modeling for the design of user interfaces • Analysis example • Requirements analysis document template • Non-Functional Requirements • Requirements analysis model validation (in Appendix) Visual modeling in UML?

3. Dynamic Modeling with UML • Diagrams for dynamic modeling • Interaction diagramsdescribe the dynamic behavior between objects • Statechartsdescribe the dynamic behavior of a single object • Interaction diagrams • Sequence Diagram: • Dynamic behavior of a set of objects arranged in time sequence. • Good for real-time specifications and complex scenarios • Collaboration Diagram : • Shows the relationship among objects. Does not show time • State Chart Diagram: • A state machine that describes the response of an object of a given class to the receipt of outside stimuli (Events). • Activity Diagram: A special type of statechart diagram, where all states are action states (Moore Automaton) What object?

4. Dynamic Modeling See the definition on the previous slide – consistent? • Definition of dynamic model: • A collection of multiple state chart diagrams, one state chart diagram for each class with important dynamic behavior. • Purpose: • Detect and supply methods for the object model • How do we do this? • Start with use case or scenario • Model interaction between objects => sequence diagram • Model dynamic behavior of a single object => statechart diagram This is somewhat over-simplified. Why?

5. An Example • Flow of events in a “Get SeatPosition” use case : 1. Establish connection between smart card and onboard computer 2. Establish connection between onboard computer and sensor for seat 3. Get current seat position and store on smart card • Which are the objects? What would this be for? What would be the concerns of the end user?

6. Sequence Diagram for “Get SeatPosition” Seat Onboard Computer Smart Card • 1. Establish connection between smart card and onboard computer • 2. Establish connection between onboard computer and sensor for seat • 3. Get current seat position and store on smart card Establish Connection Establish Connection Accept Connection Accept Connection Get SeatPosition “500,575,300” time Is this a good Sequence Diagram? --- next slide

7. Heuristics for Sequence Diagrams • Layout: • 1st column: Should correspond to the actor who initiated the use case • 2nd column: Should be a boundary object • 3rd column: Should be the control object that manages the rest of the use case • Creation: • Control objects are created at the initiation of a use case • Boundary objects are created by control objects • Access: • Entity objects are accessed by control and boundary objects, • Entity objects should never call boundary or control objects: This makes it easier to share entity objects across use cases and makes entity objects resilient against technology-induced changes in boundary objects. What are the diagrammatic conventions?

8. Is this a good Sequence Diagram? Seat Onboard Computer Smart Card • First column is not the actor • It is not clear where the boundary object is • It is not clear where the control object is Establish Connection Establish Connection Accept Connection Accept Connection Get SeatPosition “500,575,300”

9. What else can we get out of sequence diagrams? Is this really true? Is automatic derivation possible, then? • Sequence diagrams are derived from the use cases. We therefore see the structure of the use cases. • The structure of the sequence diagram helps us to determine how decentralized the system is. • We distinguish two structures for sequence diagrams: Fork and Stair Diagrams (Ivar Jacobsen)

10. Fork Diagram • Much of the dynamic behavior is placed in a single object, ususally the control object. It knows all the other objects and often uses them for direct questions and commands.

11. Stair Diagram • The dynamic behavior is distributed. Each object delegates some responsibility to other objects. Each object knows only a few of the other objects and knows which objects can help with a specific behavior. So, is there any control object then?

12. Fork or Stair? • Which of these diagram types should be chosen? • Object-oriented fans claim that the stair structure is better • The more the responsibility is spread out, the better • However, this is not always true. Better heuristics: • Decentralized control structure • Centralized control structure (better support of change) So, only 1 control object or more?

13. UML Statechart Diagram Notation Event trigger With parameters • Notation based on work by Harel • Added are a few object-oriented modifications • A UML statechart diagram can be mapped into a finite state machine State1 State2 Event1(attr) [condition]/action do/Activity Guard condition entry /action exit/action Also: internal transition and deferred events

14. State • An abstraction of the attributes of a class • State is the aggregation of several attributes a class • Basically an equivalence class of all those attribute values and links that do no need to be distinguished as far as the control structure of the system is concerned • Example: State of a bank • A bank is either solvent or insolvent • State has duration

15. coins_in(amount) / set balance Collect Money Idle coins_in(amount) / add to balance cancel / refund coins [item empty] [select(item)] [change<0] do: test item and compute change [change>0] [change=0] do: dispense item do: make change Example of a StateChart Diagram Is this a good model?

16. Nested State Diagram • Activities in states are composite items denoting other lower-level state diagrams • A lower-level state diagram corresponds to a sequence of lower-level states and events that are invisible in the higher-level diagram. • Sets of substates in a nested state diagram denote a superstate are enclosed by a large rounded box, also called contour.

17. coins_in(amount) / set balance Collect Money Idle coins_in(amount) / add to balance cancel / refund coins [item empty] [select(item)] [change<0] Superstate do: test item and compute change [change>0] [change=0] do: make change Example of a Nested Statechart Diagram Is this a good model? do: dispense item Is there any other superstate?

18. arm ready arm ready Example of a Nested Statechart Diagram ‘Dispense item’ as a composite activity: ‘Dispense item’ as an atomic activity: do: move arm to row do: move arm to column do: dispense item do: push item off shelf So, how we show this nesting?

19. Modeling Concurrency Two types of concurrency 1. System concurrency • State of overall system as the aggregation of state diagrams, one for each object. Each state diagram is executing concurrently with the others. 2. Object concurrency • An object can be partitioned into subsets of states (attributes and links) such that each of them has its own subdiagram. • The state of the object consists of a set of states: one state from each subdiagram. • State diagrams are divided into subdiagrams by dotted lines.

20. Example of Concurrency within an Object Splitting control Synchronization Emitting Do: Dispense Cash taken Cash Ready Setting to r eset Up Ready Do: Eject Card Card taken Is this a good model?

21. State Chart Diagram vs Sequence Diagram • State chart diagrams help to identify: • Changes to an individual object over time • Sequence diagrams help to identify • The temporal relationship of between objects over time • Sequence of operations as a response to one or more events

22. Dynamic Modeling of User Interfaces • Statechart diagrams can be used for the design of user interfaces • Also called Navigation Path • States: Name of screens • Graphical layout of the screens associated with the states helps when presenting the dynamic model of a user interface • Activities/actions are shown as bullets under screen name • Often only the exit action is shown • State transitions: Result of exit action • Button click • Menu selection • Cursor movements • Good for web-based user interface design

23. Navigation Path Example = screen = state • Diagnostics Menu • User moves cursor to Control Panel or Graph • Graph • User selects data group and type of graph = screen = state • Control panel • User selects functionality of sensors = screen = state • Selection • User selects data group • Field site • Car • Sensor group • Time range • User selects type of graph • time line • histogram • pie chart = screen = state • Define • User defines a sensor event • from a list of events = screen = state • Disable • User can disable a sensor event from a list of sensor events • Enable • User can enable a sensor event from a list of sensor events • List of events • User selects event(s) • Visualize • User views graph • User can add data groups for being viewed • List of sensor events • User selects sensor event(s) • Link • User makes a link (doclink)

24. Let’s Do Analysis 1. Analyze the problem statement • Identify functional requirements • Identify nonfunctional requirements • Identify constraints (pseudo requirements) 2. Build the functional model: • Develop use cases to illustrate functionality requirements 3. Build the dynamic model: • Develop sequence diagrams to illustrate the interaction between objects • Develop state diagrams for objects with interesting behavior 4. Build the object model: • Develop class diagrams showing the structure of the system

25. Requirements Analysis Document Template 1. Introduction 2. Current system 3. Proposed system 3.1 Overview 3.2 Functional requirements 3.3 Nonfunctional requirements 3.4 Constraints (“Pseudo requirements”) 3.5 System models 3.5.1 Scenarios 3.5.2 Use case model 3.5.3 Object model 3.5.3.1 Data dictionary 3.5.3.2 Class diagrams 3.5.4 Dynamic models 3.5.5 User interface 4. Glossary

26. Functional Modeling Object Modeling Dynamic Modeling Summary: Requirements Analysis • 1. What are the transformations? • Create scenarios and use case diagrams • Talk to client, observe, get historical records, do thought experiments • 2. What is the structure of the system? • Create class diagrams • Identify objects. • What are the associations between them? What is their multiplicity? • What are the attributes of the objects? • What operations are defined on the objects? • 3. What is its behavior? • Create sequence diagrams • Identify senders and receivers • Show sequence of events exchanged between objects. Identify event dependencies and event concurrency. • Create state diagrams • Only for the dynamically interesting objects.

27. Non-Functional Requirements

28. Section 3.3 Nonfunctional Requirements 3.3.1 User interface and human factors 3.3.2 Documentation 3.3.3 Hardware considerations 3.3.4 Performance characteristics 3.3.5 Error handling and extreme conditions 3.3.6 System interfacing 3.3.7 Quality issues 3.3.8 System modifications 3.3.9 Physical environment 3.3.10 Security issues 3.3.11 Resources and management issues

29. Nonfunctional Requirements: Trigger Questions 3.3.1 User interface and human factors • What type of user will be using the system? • Will more than one type of user be using the system? • What sort of training will be required for each type of user? • Is it particularly important that the system be easy to learn? • Is it particularly important that users be protected from making errors? • What sort of input/output devices for the human interface are available, and what are their characteristics? 3.3.2 Documentation • What kind of documentation is required? • What audience is to be addressed by each document? 3.3.3 Hardware considerations • What hardware is the proposed system to be used on? • What are the characteristics of the target hardware, including memory size and auxiliary storage space?

30. Nonfunctional Requirements, ctd 3.3.4 Performance characteristics • Are there any speed, throughput, or response time constraints on the system? • Are there size or capacity constraints on the data to be processed by the system? 3.3.5 Error handling and extreme conditions • How should the system respond to input errors? • How should the system respond to extreme conditions? 3.3.6 System interfacing • Is input coming from systems outside the proposed system? • Is output going to systems outside the proposed system? • Are there restrictions on the format or medium that must be used for input or output?

31. Nonfunctional Requirements, ctd • 3.3.7 Quality issues • What are the requirements for reliability? • Must the system trap faults? • What is the maximum time for restarting the system after a failure? • What is the acceptable system downtime per 24-hour period? • Is it important that the system be portable (able to move to different hardware or operating system environments)? • 3.3.8 System Modifications • What parts of the system are likely candidates for later modification? • What sorts of modifications are expected? • 3.3.9 Physical Environment • Where will the target equipment operate? • Will the target equipment be in one or several locations? • Will the environmental conditions in any way be out of the ordinary (for example, unusual temperatures, vibrations, magnetic fields, ...)?

32. Nonfunctional Requirements, ctd • 3.3.10 Security Issues • Must access to any data or the system itself be controlled? • Is physical security an issue? • 3.3.11 Resources and Management Issues • How often will the system be backed up? • Who will be responsible for the back up? • Who is responsible for system installation? • Who will be responsible for system maintenance?

33. Constraints (Pseudo Requirements) • Constraint: • Any client restriction on the solution domain • Examples: • The target platform must be an IBM/360 • The implementation language must be COBOL • The documentation standard X must be used • A dataglove must be used • ActiveX must be used • The system must interface to a papertape reader

34. Appendix: Additional Slides

35. How do you find classes? • In previous lectures we have already established the following sources • Application domain analysis: Talk to client to identify abstractions • Application of general world knowledge and intuition • Scenarios • Natural language formulation of a concrete usage of the system • Use Cases • Natural language formulation of the functions of the system • Textual analysis of problem statement (Abbott) • Today we show how identify classes from dynamic models • Actions and activities in state chart diagrams are candidates for public operations in classes • Activity lines in sequence diagrams are also candidates for objects

36. Start with Flow of Events from Use Case • Flow of events from “Dial a Number” Use case: • Caller lifts receiver • Dial tone begins • Caller dials • Phone rings • Callee answers phone • Ringing stops • ....

37. What is an Event? • Something that happens at a point in time • Relation of events to each other: • Causally related: Before, after, • Causally unrelated: concurrent • An event sends information from one object to another • Events can be grouped in event classes with a hierarchical structure. ‘Event’ is often used in two ways: • Instance of an event class: “New IETM issued on Thursday September 14 at 9:30 AM”. • Event class “New IETM”, Subclass “Figure Change” • Attribute of an event class • IETM Update (9:30 AM, 9/14/99) • Car starts at ( 4:45pm, Monroeville Mall, Parking Lot 23a) • Mouse button down(button#, tablet-location)

38. Sequence Diagram • From the flow of events in the use case or scenario proceed to the sequence diagram • A sequence diagram is a graphical description of objects participating in a use case or scenario using a DAG (direct acyclic graph) notation • Relation to object identification: • Objects/classes have already been identified during object modeling • Objects are identified as a result of dynamic modeling • Heuristic: • A event always has a sender and a receiver. • The representation of the event is sometimes called a message • Find them for each event => These are the objects participating in the use case

39. Power is turned on Car moves forward and car headlight shines Power is turned off Car stops and headlight goes out. Power is turned on Headlight shines Power is turned off Headlight goes out. Power is turned on Car runs backward with its headlight shining. Power is turned off Car stops and headlight goes out. Power is turned on Headlight shines Power is turned off Headlight goes out. Power is turned on Car runs forward with its headlight shining. Problem Statement: Direction Control for a Toy Car

40. Find the Functional Model: Do Use Case Modeling • Use case 1: System Initialization • Entry condition: Power is off, car is not moving • Flow of events: • Driver turns power on • Exit condition: Car moves forward, headlight is on • Use case 2: Turn headlight off • Entry condition: Car moves forward with headlights on • Flow of events: • Driver turns power off, car stops and headlight goes out. • Driver turns power on, headlight shines and car does not move. • Driver turns power off, headlight goes out • Exit condition: Car does not move, headlight is out

41. Use Cases continued • Use case 3: Move car backward • Entry condition: Car is stationary, headlights off • Flow of events: • Driver turns power on • Exit condition: Car moves backward, headlight on • Use case 4: Stop backward moving car • Entry condition: Car moves backward, headlights on • Flow of events: • Driver turns power off, car stops, headlight goes out. • Power is turned on, headlight shines and car does not move. • Power is turned off, headlight goes out. • Exit condition: Car does not move, headlight is out. • Use case 5: Move car forward • Entry condition: Car does not move, headlight is out • Flow of events • Driver turns power on • Exit condition: • Car runs forward with its headlight shining.

42. Use Case Pruning • Do we need use case 5? • Use case 1: System Initialization • Entry condition: Power is off, car is not moving • Flow of events: • Driver turns power on • Exit condition: Car moves forward, headlight is on • Use case 5: Move car forward • Entry condition: Car does not move, headlight is out • Flow of events • Driver turns power on • Exit condition: • Car runs forward with its headlight shining.

43. Find the Dynamic Model: Create sequence diagram • Name: Drive Car • Sequence of events: • Billy turns power on • Headlight goes on • Wheels starts moving forward • Wheels keeps moving forward • Billy turns power off • Headlight goes off • Wheels stops moving • . . .

44. :Wheel :Headlight Billy:Driver Power(on) Power(on) Power(off) Power(off) Power(on) Power(on) Sequence Diagram for Drive Car Scenario

45. Headlight Off power power on off On Toy Car: Dynamic Model Wheel Forward power power off on Stationary Stationary power power on off Backward

46. Power Status: (On, Off) TurnOn() TurnOff() Toy Car: Object Model Car Wheel Headlight Status: (On, Off) Motion: (For ward, Backward, Switch_On() Stationary) Switch_Off() Star t_Moving() Stop_Moving()

47. Additional constraints in ARENA Project • Interface Engineering • Provide ARENA players with access to an existing game: Bumpers • Complete Java Code for Bumpers posted on SE Discuss • Greenfield Engineering • Design a new game and provide ARENA players with access to the new game • Constraints: • Extensibility • Scalability • Additional Constraint: • The existing ARENA code does not have to be recompiled when the new game is introduced • ARENA does not have to be shut down (currently running games can continue) when the new game is introduced • Is the “NotShutDown” requirement realistic?

48. Impact on ARENA Object Model New System Legacy System

49. Le v el 1 User tasksdescribe application domain Le v el 2 Le v el 2 Le v el 3 Le v el 3 Le v el 3 Use Casesdescribe interactions Le v el 4 Le v el 4 Servicesdescribe system Participating Objectsdescribe domain entities Clarification: Terminology in REQuest A B

50. ARENA user tasks (top level use cases)